I suppose all this arises from England having no really hot summer, so no reason for creating patterns specific to fabrics other than wool. Madras is from India I believe? I don't know the history of seersucker, striped blazers, and gingham check, but I'd guess they're not English.

The english have a history of wearing jackets in really loud stripes for things like school uniforms, and specifically regattas- actually, that's what the word "blazer" originally referred to before it came to encompass the jackets with metal buttons we know today.

They are not garments to be taken too seriously:

I've actually seen one of those being worn in the wild. A few years ago, the President of my now alma mater showed up in one pretty much randomly. I asked him about it, apparently the rowing team alumni group had ordered a bunch for their reunion and given one to him for kicks. Green and cream with the University seal on it, it was awesome.

^I knew the part about the relation to the word "blazer" but for some reason I thought it was an Ivy thing. Guess I was wrong. Anyway, as you said, not a serious garment. I still think my general theory of there being few real patterns reserved or mostly associated with summer jacketing having something to do with there being little reason to deviate from wool in an English summer. Or perhaps just that all linen/cotton or blends thereof does not take well to patterns, which I understand to be Manton's position, at least in the case of pure linen.